This is a Phase Ⅲ, randomized, double-blind, active-controlled study to assess the immunogenicity and safety of the varicella vaccine,Live (hereinafter referred to as "varicella vaccine")manufactured by Sinovac (Dalian) Vaccine Technology Co., LTD.(hereinafter referred to as "Sinovac").

A total of 642 healthy participants aged 12~15 months will be enrolled. All participants will be randomized at a 1:1 ratio to receive a single dose of varicella vaccine either manufactured by Sinovac (Group A) or Merck Sharp & Dohme (MSD, Group B).

Inclusion Criteria:

• Healthy children aged 12~15 months;
• Participants' legal guardians are able to understand and sign the informed consent voluntarily;
• Participants are able to comply with the study procedures based on the assessment of the investigator;
• Participants should provide verifiable identification, to be contacted, and to contact the investigator during the study period.

Exclusion Criteria:

• Prior vaccination with any varicella containing vaccines;
• Prior history of VZV infection;
• Known allergy to vaccines or vaccine ingredients, or serious adverse reactions to vaccines, such as urticaria, dyspnea, angioneurotic edema;
• Autoimmune diseases (including but not limited to systemic lupus erythematosus, rheumatoid arthritis, etc.) or immunodeficiency/immunosuppression (such as HIV infection, organ transplantation), asplenia;
• Receipt of blood products or immunoglobulins within the past 3 months before enrollment in this study, or scheduled to receive these treatments during the study period;
• Receipt of other investigational vaccines within 30 days prior to vaccination in this study;
• Receipt of attenuated live vaccines within 28 days prior to vaccination in this study;
• Receipt of inactivated or subunit vaccines within 7 days prior to vaccination in this study;
• Acute onset of various acute diseases or chronic diseases within 7 days prior to vaccination in this study;
• Has fever on the day of vaccination, with the axillary temperature >37°C before vaccination;
• Is participating in or planning to participate in other vaccine or drug clinical trials;
• Any confirmed or suspected syphilis, hepatitis B or hepatitis C infection;
• According to the investigator's judgment, the subject has any other factors that might interfere with the clinical trial results or pose additional risk to the participant due to participation in the study.